Marine Science 2014, 4(1): 10-20
DOI: 10.5923/j.ms.20140401.02
Benthopelagic Shrimp and Associated Pelagic and
Benthopelagic Fauna on a Bowhead Whale Foraging
Ground in Disko Bay, West Greenland
Ole Gorm Norden Andersen1,*, Kristin L. Laidre2, Mads Peter Heide-Jørgensen3
1
Department of Bioscience, Aarhus University, Roskilde, 4000, Denmark
Polar Science Center, APL/University of Washington, Seattle, WA98105-6698, USA
3
Greenland Institute of Natural Resources, Nuuk, 3900, Greenland
2
Abstract Bowhead whales (Balaena mysticetus) congregate annually in Disko Bay, West Greenland prior to and during
the spring phytoplankton bloom. We investigated the benthopelagic and associated pelagic fauna at 25 – 200 m depth during
the spring of 2008 and 2009 in an area where foraging whales have often been observed. The benthopelagic and associated
pelagic fauna > 0.5 mm in greatest body dimension was dominated by Crustacea which comprised 95 % of a total wet weight
biomass of 2.1 ± 1.7 g m-3, and included at least 15 species of Caridea ≥ 5 mm (1.6 ± 1.5 g m-3) which comprised almost
100 % of Caridean, 81 % of Crustacean, and 77 % of total wet weight biomass m-3. Three groups of organisms ≥ 5 mm
(Caridea, Mysida, and Pisces) made up 94 % of total wet weight biomass. Together, Copepoda, Amphipoda, Caridea, and
Mysida made up 96 % of the total abundance of 63 ± 103 specimens m-3. Copepods averaged 42 % of total abundance. There
was a general decrease in biomass and abundance with increasing depth, mainly due to Caridea, Mysida, and Amphipoda.
Pisces and Copepoda had greatest biomass and were most abundant at intermediate depths (50-100 m). The size of most of
the largest and most abundant species of Caridea and Pisces increased with depth. This is among the first detailed
examinations of a bowhead whale foraging ground in the Arctic and the first comprehensive description of benthopelagic and
associated pelagic fauna in West Greenland.
Keywords Shrimp, Bowhead whale, West Greenland
1. Introduction
Every year in late winter and spring (March to May),
approximately 1200 bowhead whales (Balaena mysticetus)
arrive in Disko Bay, West Greenland (Figure 1) to feed on
dense concentrations of copepods which thrive on a massive
spring phytoplankton bloom that occurs just after the sea ice
breaks up[1][2]. The spring bloom occurs over a 2-3 week
period peaking between mid April and late May in the upper
15-40 m of the water column with a maximum peak at 5-10
m[3][4][1]. Although maximum diving depths for bowhead
whales in the Disko Bay area exceed 400 m, most whale
diving activity targets depths between 50 and 100 m[1]. This
suggests some flexibility in bowhead feeding patterns and
* Corresponding author:
[email protected] (Ole Gorm Norden Andersen)
Published online at http://journal.sapub.org/ms
Copyright © 2014 Scientific & Academic Publishing. All Rights Reserved
whales may in fact employ different strategies depending on
the copepod cycle and timing of the spring bloom. Bowheads
are known to feed close to the bottom in the bay Laksebugten
in the northern Disko Bay off the south coast of Disko Island
and likely target benthopelagic and associated organisms
including dense swarms of lipid-rich copepods that are
diapausing near the bottom[5][6]. Later in spring, whales
may target copepods that ascend to couple with the spring
bloom, requiring shallower dives but perhaps more water
filtration.
This study reports the first detailed characterization of the
benthopelagic (living both on and close to the bottom) and
associated pelagic fauna in West Greenland. We quantify
size, distribution, density, and biomass of taxonomic groups
and entities of fauna > 0.5 mm in a portion of Disko Bay
(25-200 m) where bowhead whales appear to feed
intensively and seemingly close to the bottom prior to and
during the spring bloom.
Marine Science 2014, 4(1): 10-20
11
2. Material and Methods
Bottom-near benthopelagic and pelagic fauna > 0.5 mm
was sampled between 18 April and 1 May 2008 and on 27
April 2009 at depths of 25–200 m. Samples were collected in
and off the bay Laksebugten in northern Disko Bay off the
south coast of Disko Island, West Greenland, in a ~ 100 km2
area centered at ~ 69.27oN, 54oW (Figure 2).
Purely benthic organisms were not sampled. The bottom
in the area consists largely of undulating stone strewn
iceberg-scoured rock with a rich algal flora and epifauna of,
notably, scallops and sea urchins. The outer parts are
exposed to iceberg-laden currents primarily sweeping out of
Disko Bay. Due to a marked halocline created by glacier
run-off and the melting icebergs leaving Disko Bay, a small
river feeding into the bay exerts little influence on conditions
at the depths concerned.
Twenty-nine samples were collected in 2008 and 10 in
2009 with an epibenthic sledge (KC-Denmark) (Figure 3).
Figure 1. Bathymetric map of Disko Bay, West Greenland with place
names mentioned in the text
Figure 2. The sampling area in and off Laksebugten centered at ~ 69.27oN, 54oW with depth contours 50 m, 100 m, and 200 m, and predicted (krigged)
distribution of biomass and biomass at each station of benthopelagic and pelagic fauna caught with a 0.5 mm mesh epibenthic sledge (Figure 3) in g m-3
shown
12
Ole Gorm Norden Andersen et al.: Benthopelagic Shrimp and Associated Pelagic and Benthopelagic
Fauna on a Bowhead Whale Foraging Ground in Disko Bay, West Greenland
Figure 3. KC epibenthic sledge, side view diagram without net and in natura being deployed open, as release arm hits deck
The sledge had a 0.175 m2 (70 cm wide and 25 cm high)
opening and was towed ~ 0-15 cm above the sea floor. The
sledge sampled the lower ~ 25-40 cm of the water column
with a 0.5mm mesh 4 m long conical net towed 245-697 m
(measured from start to stop GPS positions) at a speed of ~
1-1.5 knots. After it was deployed from the side of a 30 m
long vessel (rv Porsild), the opening was closed until the
sledge reached the bottom and was closed again while the
sledge was brought to the surface. Sledge samples are biased
towards slower moving species and this bias could not be
quantified. A brief video recording documented avoidance
behavior of organisms in front of the sledge. At each of the
stations sampled in 2008, a 0.2 mm mesh (available at the
time) and 0.25 m2 opening WP2 plankton net with a 0.5 mm
mesh cod end was towed at ~ 1 m sec-1 from the bottom to the
surface in order to document whether Calanus species were
still concentrated near the bottom.
All organisms were counted and weighed immediately or
following fixation in 4 % formaldehyde in seawater
neutralized with borax and subsequent preservation in 70 %
alcohol. Organisms in the sledge samples were divided into
two size classes: ≥ 5 mm (excluding virtually all copepoda
other than Calanus hyperboreus copepodite 4 to adult) and
< 5 mm in greatest body dimension. Faunal entities included
the two size classes ≥ 5 mm and < 5 mm, taxonomic entity
(lowest taxonomic level (e.g. species, order, class, etc.) and
taxonomic group (encompassing two or more taxonomic
entities, e.g. species of Caridea). All Pisces[7], Caridea[8][9],
Euphausiacea[10], and Amphipoda Hyperiidea[11] ≥ 5 mm
were determined to species. Organisms in the WP2 net
samples were determined to a higher taxonomic level and
weighed. Only Caridea ≥ 5 mm and Gastropoda were
determined to species, and, like Mysida, Chaetognatha, and
Coelenterata, they were also counted. There was no visual
evidence of clogging of nets and wet weight biomass in g m-3
and abundance m-3 were calculated assuming no clogging.
Results were grouped successively in 4 bins of 8 and one of 7
and total covering the depth spans 25–49 m, 41–70 m, 55–88
m, 75–124 m, 128–200 m, and 25-200 m respectively
(Figure 4). Statistics (Excel) for each category include mean
(AV), maximum (MAX), minimum (MIN), and standard
deviation (SD). Data were mapped using ArcGIS (ESRI).
The Geostatistical Analyst extension was used to develop
interpolated density surfaces for all benthopelagic and
associated pelagic organisms using ordinary krigging
(Figure 2).
3. Results
3.1. Sledge Samples
3.1.1. General
Average wet weight biomass per station was 2.1 ± 1.7 g
m-3 (Table 1). The size category ≥ 5 mm dominated biomass
with 98±4% of the mean due almost exclusively to Crustacea
contributing 92 ± 11 % and particularly to Crustacea of the
infra-order Caridea contributing 77 ± 27% and the order
Mysida contributing 12 ± 22% but also to Pisces contributing
5.5 ± 9.7 % to the mean.
Average total abundance per station was 65 ± 111
organisms m-3. Organisms < 5 mm dominated with 78 ± 36%
of the mean. Crustacea of all sizes dominated with 100 ± 2 %
of the mean due primarily to Copepoda, Amphipoda, Caridea,
and Mysida which together contributed 96 ± 6 % to the mean
(Table 1).
Total biomass (coefficient of variation (CV) 78 %) and
abundance (CV 59 %), like those of the major taxonomic
entities, varied greatly among stations. Total biomass
decreased between 25 and 200 m from 2.8 to 0.5 g m-3 (r 0.34,
p < 0.05) and from 88 to 11 organisms m-3 (r 0.22, p < 0.001).
The total biomass was greatest in the depth range 41-70 m
primarily due to Caridea. Total abundance was greatest in the
shallowest depth bin (25-49 m) primarily due to Crustacea
< 5 mm (Figure 4A). Due to observed avoid-ance in front of
the sledge, biomass and abundance of larger organisms such
as Pisces, Caridea, and Euphausiacea ≥ 5 mm should be
regarded as minimum values.
Marine Science 2014, 4(1): 10-20
13
Table 1. Average, maximum, minimum and standard deviation of wet weight biomass in g m-3 and abundance m-3 of faunal entities (size categories and
taxonomic entities and groups (underlined)) in 0.5 mm KC epibenthic sledge samples from 25–200 m deep stations (n=39) in and off Laksebugten in the
northern Disko Bay off the south coast of Disko Island, West Greenland 18 April to 1 May 2008 - 9
Faunal entities in sledge samples
size categories and taxonomic entities and
groups
sample hits
Wet weight biomass in g m-3
Specimen number m-3
AV
MAX
MIN
SD
AV
MAX
MIN
SD
all entities
39
2.1
7.2
0.3
1.7
65.3
597.0
1.1
110.5
entities ≥ 5 mm
39
2.1
7.1
0.2
1.6
14.1
118.6
0.7
23.3
Pisces ≥ 5 mm
27
0.1
0.6
0.0
0.2
0.1
0.6
0.0
0.1
Anarchichas lupus
1
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
Anarchichas minor
1
0.0
0.2
0.0
0.0
0.0
0.0
0.0
0.0
Anisarchus medius
16
0.0
0.3
0.0
0.1
0.1
0.5
0.0
0.1
Artediellus atlanticus
1
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
Aspidophoroides monopterygius
1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Cyclopteropsis mcalpini
1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Eumicrotremus spinosus
1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Gymnocanthus tricuspis
3
0.0
0.1
0.0
0.0
0.0
0.1
0.0
0.0
Hippoglossoides platessoides
8
0.0
0.4
0.0
0.1
0.0
0.0
0.0
0.0
Icelus bicornis
3
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Icelus sp.
2
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Icelus spatula
11
0.0
0.1
0.0
0.0
0.0
0.1
0.0
0.0
Leptagonus decagonus
1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Leptoclinus maculatus
3
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
Myoxocephalus scorpius
3
0.0
0.2
0.0
0.0
0.0
0.0
0.0
0.0
Ulcina olrikii
2
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Caridea ≥ 5 mm
39
1.6
7.1
0.0
1.5
5.2
57.5
0.1
9.3
Argis dentata
36
0.3
1.9
0.0
0.4
2.0
55.4
0.0
8.8
Eualus belcheri
28
0.1
1.4
0.0
0.3
0.2
1.7
0.0
0.4
Eualus fabricii
33
0.6
5.8
0.0
1.3
1.7
16.6
0.0
3.4
Eualus gaimardii
2
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Eualus macilentus
1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Eualus stoneyi
4
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Eualus sp.
2
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Lebbeus groenlandicus
1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Lebbeus polaris
19
0.0
0.5
0.0
0.1
0.1
0.8
0.0
0.2
Pandalus borealis
29
0.4
2.1
0.0
0.5
0.8
5.5
0.0
1.2
Pandalus montagui
17
0.0
0.0
0.0
0.0
0.0
0.2
0.0
0.0
Sabinea septemcarinata
6
0.0
0.1
0.0
0.0
0.0
0.1
0.0
0.0
Sclerocrangon boreas
9
0.1
1.0
0.0
0.2
0.1
0.8
0.0
0.2
Spirontocaris lilljeborgii
2
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Spirontocaris phippsii
6
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
Spirontocaris spinus
34
0.1
0.5
0.0
0.1
0.3
1.8
0.0
0.4
Caridea juv. ≥ 5 mm
2
0.0
0.0
0.0
0.0
0.0
0.4
0.0
0.1
Euphausiacea ≥ 5 mm
3
0.0
0.2
0.0
0.0
0.1
1.9
0.0
0.3
Euphausiacea indet. ≥ 5 mm
1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
14
Ole Gorm Norden Andersen et al.: Benthopelagic Shrimp and Associated Pelagic and Benthopelagic
Fauna on a Bowhead Whale Foraging Ground in Disko Bay, West Greenland
Faunal entities in sledge samples
size categories and taxonomic entities and
groups
sample hits
Wet weight biomass in g m-3
Specimen number m-3
AV
MAX
MIN
SD
AV
MAX
MIN
SD
Thysanoessa inermis
2
0.0
0.1
0.0
0.0
0.0
1.0
0.0
0.2
Thysanoessa longicaudata
1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Thysanoessa raschii
1
0.0
0.1
0.0
0.0
0.0
0.9
0.0
0.1
Mysida ≥ 5 mm
26
0.3
3.6
0.0
0.7
4.5
67.2
0.0
12.7
Mysida indet. ≥ 5 mm
23
0.3
3.6
0.0
0.7
4.5
67.2
0.0
12.7
Erythrops sp.
1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Stilomysis grandis
2
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
Amphipoda ≥ 5 mm
31
0.1
0.8
0.0
0.2
2.0
35.0
0.0
7.5
Parathemisto libellula
1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Amphipoda (benthopelagic) ≥ 5mm
31
0.0
0.8
0.0
0.2
2.0
35.0
0.0
7.5
Copepoda ≥ 5 mm
21
0.0
0.4
0.0
0.1
2.1
30.5
0.0
5.3
Cumacea ≥ 5 mm
5
0.0
0.0
0.0
0.0
0.0
0.6
0.0
0.1
non-crustacean invertebrates ≥ 5 mm
13
0.0
0.0
0.0
0.0
0.1
1.9
0.0
0.4
Chaetognatha ≥ 5 mm
8
0.0
0.0
0.0
0.0
0.1
1.9
0.0
0.4
Medusae ≥ 5 mm
4
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
Pisces larvae < 5 mm
3
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
Pisces ovae < 5 mm
4
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
Crustacea < 5 mm
23
0.0
0.4
0.0
0.1
51.1
538.8
0.0
99.7
Caridea juv. < 5 mm
15
0.0
0.0
0.0
0.0
7.1
69.6
0.0
15.7
Euphausiacea juv. < 5 mm
1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Mysida juv. < 5 mm
6
0.0
0.0
0.0
0.0
2.7
42.0
0.0
9.3
Amphipoda, Hyperiidea juv. < 5 mm
7
0.0
0.0
0.0
0.0
0.0
0.4
0.0
0.1
Amphipoda (benthopelagic) < 5 mm
20
0.0
0.1
0.0
0.0
13.8
437.3
0.0
69.9
Cirripedia cypris < 5 mm
2
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Copepoda < 5 mm
19
0.0
0.4
0.0
0.1
25.4
312.7
0.0
55.2
Cumacea < 5 mm
15
0.0
0.0
0.0
0.0
2.0
59.5
0.0
9.7
Isopoda < 5 mm
7
0.0
0.0
0.0
0.0
0.1
2.8
0.0
0.5
Ostracoda < 5 mm
1
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
Tanaidacea < 5 mm
1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
non-crustacean invertebrates < 5 mm
6
0.0
0.0
0.0
0.0
0.1
0.5
0.0
0.1
Bivalvia larvae < 5 mm
2
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
Limacina helicina
3
0.0
0.0
0.0
0.0
0.0
0.2
0.0
0.0
Gastropoda larvae < 5 mm
1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Holothuria larvae < 5 mm
1
0.0
0.0
0.0
0.0
0.0
0.2
0.0
0.0
Polychaeta larvae < 5 mm
4
0.0
0.0
0.0
0.0
0.0
0.5
0.0
0.1
3.1.2. Crustacea
Crustacea ≥ 5 mm dominated both total biomass with 92 ± 11 % and Crustacean biomass with 98 ± 5 % in all samples,
whereas Crustacea < 5 mm, found in 82 % of samples, dominated total abundance with a mean of 78 ± 36% of total
abundance in 56 % of samples and Crustacean abundance with a mean of 79 ± 36 % of crustacean abundance in 59 % of
samples (Table 1).
Marine Science 2014, 4(1): 10-20
15
Figure 4. Five depth-binned densities (by increasing depth) and total mean of faunal entities and size categories in epibenthic sledge samples (N=39) taken
in and off the bay Laksebugten, Disko Island, West Greenland 18 April to 1 May 2008 and 27 April 2009 are shown as wet weight biomass in g m-3 (left) and
abundance m-3 (right). Eight stations contributed to each of the first four depth bins, 7 to the fifth and all stations contributed to the last. A: All faunal entities
(except minor Crustacean groups ≥ 5 mm), B: Caridea ≥ 5 mm, C: Pisces ≥ 5 mm. Mean depth and depth span of each bin is shown below the pillars in C
16
Ole Gorm Norden Andersen et al.: Benthopelagic Shrimp and Associated Pelagic and Benthopelagic
Fauna on a Bowhead Whale Foraging Ground in Disko Bay, West Greenland
3.1.3. Caridea
Fifteen species of Caridea ≥ 5 mm and < 9.5 mm long
were identified in the sledge samples (Table 1). Most of them
are of widespread Boreal to High Arctic occurrence and the
depth distributions corresponded to those reported in the
literature (Rathbun 1929, Squires 1990), except for Eualus
belcheri which was also found at shallower depths and E.
stoneyi which was found exclusively at greater depth (Table
2). Caridea were found in all samples and was the third most
abundant taxonomic group - excluding Crustacea as a whole.
Apart from Crustacea as a whole, Caridea ≥ 5 mm was the
only taxonomic group found in all samples. Caridea ≥ 5 mm
dominated both total Crustacean (81 ± 28 %) and Caridean
(100 ± 0.4 %) biomass greatly. Caridea ≥ 5 mm dominated
total biomass in 82 % of samples. In nearly half (44 %) of
these they made up over 90 % of biomass and in 90 % of all
samples they were the dominant taxonomic entity. Caridea
< 5 mm occurred in 39 % of samples only and contributed
marginally to total biomass with 0.2 ± 0.3 %. With 58 ± 34 %
of Caridean numbers, they were slightly more abundant than
Caridea ≥ 5 mm, but contributed little to total abundance (11
± 22 %) (Table 1).
The biomass of Caridea ≥ 5 mm peaked in the second
shallowest depth bin (41–70 m), primarily due to E. fabricii,
and was lowest in the deepest depth bin (128–200 m) (Figure
4B). The abundance of Caridea decreased from the
shallowest depth bin (25-49 m) to the deepest (128-200 m)
and linearly from 9.2 organisms m-3 at 25 m to -3.6
organisms m-3 at 200 m (r 0.34, p < 0.05). The mean size of
Caridea ≥ 5 mm (Table 2) increased linearly from 0.34 g at
25 m to 0.88 g at 200 m (r 0.41, p < 0.01), with a mid-depth
maximum at ~ 120 m (Figure 5).
The five most widely distributed species of Caridea ≥ 5
mm within the investigation area (each found in 72 – 87 % of
samples (Table 2)) were also the most abundant species and
those with greatest total biomass (Table 1). The four species
with greatest total biomass dominated total biomass and the
biomass of Caridea ≥ 5 mm in up to 21 % of samples,
contributing up to 90 % to total sample biomass and up to
91 % to sample biomass of Caridea ≥ 5 mm. No single
species dominated total abundance in any single sample.
Amongst the three species that dominated biomass and
abundance of Caridea ≥ 5 mm the most, the biomass of E.
fabricii followed the same depth distribution pattern as all
Caridea ≥ 5 mm, peaking at 41–70 m and with lowest values
at 128–200 m, whereas P. borealis and A. dentata peaked at
55–88 m and had their lowest values at 25–49 m and
128–200 m respectively (Figure 4B). Amongst the three, A.
dentata dominated abundance and especially at 25–49 m, E.
fabricii dominated and peaked at 41–70 m, and P. borealis
dominated and peaked at 55–88 m (Figure 4B). There was a
general increase in size with depth of Caridea ≥ 5 mm and of
the two most abundant species E. fabricii and A. dentata, of
which only the smallest specimens were found at the
shallowest depths (Figure 5).
Figure 5. Mean specimen size in g of A) Caridea ≥ 5 mm (N = 39) and B)
and C) the two species also showing a significant (p < 0.001) increase in size
with depth (B (N = 33)) (C (N = 34)) at epibenthic sledge stations in and off
the bay Laksebugten, Disko Island, West Greenland 18 April to 1 May 2008
and 27 April 2009
3.1.4. Mysida
Mysida were found in 67 % of samples and constituted the
fourth most abundant taxonomic group (excluding Crustacea
as a whole). They contributed to a minor extent to both total
and Crustacean abundance (both 11 ± 23 %). A species and a
genus of Mysida ≥ 5 mm were identified (Table 1), but in
most samples, these relatively small (< 2 cm long) Crustacea
were not determined to species. Mysida ≥ 5 mm, also found
in 67 % of samples, constituted the taxonomic group ≥ 5 mm
with the second largest mean biomass m-3 (12 ± 22 % of total)
and they were more abundant than Mysida < 5 mm (7 ± 19 %
compared to 4 ± 9 %). Mean biomass of Mysida < 5 mm,
occurring in 15 % of samples, was negligible (0.04 ± 0.1 %).
Mysida were caught almost exclusively at depths shallower
than 50 m (Figure 4A).
3.1.5. Amphipoda
Crustacea of the order Amphipoda were found in 87 % of
samples and contributed to a minor extent to total biomass (3
Marine Science 2014, 4(1): 10-20
± 7 %) (Table 1). They were the second most abundant
taxonomic group after Copepoda (24 ± 16 % of total).
Amphipoda ≥ 5 mm were found in 95 % of samples and
dominated Amphipodan biomass to a great extent (88 ±
35 %). Amphipoda < 5 mm, found in 74 % of samples,
dominated Amphipodan abundance (87 ± 39 %) and
contributed substantially to total abundance (21 ± 14 %). The
pelagic Amphipoda, Hyperiidea were found in 18 % of
samples, and adults ≥ 5 mm (1 species (Table 1)) were only
found in one sample. Like Mysida, Amphipoda were caught
almost exclusively at depths shallower than 50 m and
biomass and abundance declined with increasing depth with
a distinct minimum at ~ 125 m (Figure 4A). There were some
exceptionally high estimates of biomass and abundance at 25
m, where Amphipoda < 5 mm were particularly abundant
(Table 1).
17
values of both found at 50-100 m and one exceptionally high
value at 100 m (Table 1, Figure 6A).
3.1.7. Euphausiacea
Crustacea of the order Euphausiacea were found in four
sledge samples only, of which three contained adults ≥ 5 mm
(three species (Table 1)), contributing 0.3 ± 10 % to mean
biomass and 0.08 ± 3 % to mean abundance, whereas the
fourth contained only one juvenile < 5 mm.
3.1.8. Pisces
3.1.6. Copepoda
Figure 6. Wet weight biomass in g m-3 of all Copepoda in A) sledge tows
relative to mean station depth and B) WP2 net bottom to surface tows
relative to station depth (N = 29) in and off the bay Laksebugten, Disko Bay,
West Greenland 18 April to 1 May 2008
Crustaceans of the order Copepoda – almost exclusively
Calanus species - were found in 82 % of samples. The mean
biomass m-3 was slightly less than that of Amphipoda (2.7 ±
8 % of total), whereas mean abundance was almost double
that of Amphipoda and the greatest among all taxonomic
groups (42 ± 37 % of total) (Table 1). Copepoda ≥ 5 mm
occurred in 54 % of samples, whereas Copepoda < 5 mm
occurred in 72 % and dominated both Copepodan biomass
(63 ± 35 %) and abundance (92 ± 33 %) and contributed
substantially to total abundance (39 ± 36 %). Copepoda
occurred at all depths (Figure 4A). Their biomass and
abundance increased insignificantly with depth, with greatest
Figure 7. Mean specimen size in g A) of Pisces ≥ 5 mm (N = 39) and B)
and C) of the two Pisces species also showing a significant (p < 0.001)
increase in size with depth (B (N = 16), C (N = 11)) at epibenthic sledge
stations in and off the bay Laksebugten, Disko Island, West Greenland 18
April to 1 May 2008 and 27 April 2009
Fifteen species of Pisces ≥ 5 mm and < 15 cm long were
identified in the sledge samples (Table 1). Most of them are
of widespread Boreal to High Arctic occurrence and their
depth distribution matches those previously recorded[7].
Only the High Arctic Cyclopteropsis mcalpini has not
previously been recorded south of Melville Bay. Pisces ≥ 5
mm were found in 69 % of samples, and even though they
18
Ole Gorm Norden Andersen et al.: Benthopelagic Shrimp and Associated Pelagic and Benthopelagic
Fauna on a Bowhead Whale Foraging Ground in Disko Bay, West Greenland
contributed the third largest biomass of taxonomic groups ≥
5 mm (5 ± 10 % of total), they were not the dominant group ≥
5 mm at any station. Mean biomass and abundance of Pisces
< 5 mm, occurring in 13 % of samples only, was negligible
(biomass 0.002 ± 0.02 % and abundance 0.00005 ± 0.0002 %
of total). The two most abundant species, Anisarchus medius
and Icelus spatula, were also the most widely distributed,
occurring in 41 % and 28 % of samples respectively.
Together they made up 81 ± 43% of abundance and
48 ± 46% of biomass of Pisces ≥ 5 mm. Pisces ≥ 5 mm
occurred at all depths with a slight overall increase in
biomass with depth and highest biomasses at ~ 75-100 m
depth (Figure 4C). Abundance decreased slightly overall
with increasing depth, with highest abundances at ~ 50–100
m depth (Figure 4C). Changes with depth in biomass and
abundance of the two most abundant fish species, A. medius
and I. spatula, were quite similar to those of all Pisces ≥ 5
mm. The mean size of Pisces ≥ 5 mm and of A. medius and I.
spatula (Table 2) increased with depth (Figure 7).
Table 2. Average, maximum, minimum and standard deviation of wet weight biomass in g of Caridea and Pisces ≥ 5 mm arranged by decreasing
occurrence (% sample hits) respectively in KC epibenthic sledge samples from 25–200 m deep stations (n=39) in and off Laksebugten in northern Disko Bay
off the south coast of Disko Island, West Greenland 18 April to 1 May 2008 - 9. Minimum and maximum mean sample depths and depth spans recorded in
the literature are shown, and geographical distributions are given tentatively as High Arctic (HA) = central Canadian Arctic and northwestern Baffin Bay,
Low Arctic (LA) = down to and including coastal waters around New Foundland and the southern tip of Greenland, and Boreal (B) = further south[7][8][9]
%
sample hits
Mean specimen wet weights in
grams
Mean
sample depths
in m
MAX
Recorded
depths of
occurrence
in m
MIN
MAX
Geographical
distribution
AV
MAX
MIN
SD
MIN
Caridea
100
0.5
1.6
0.0
0.3
25
200
0
2000
B - HA
Argis dentata
92
1.2
7.9
0.0
1.7
25
152
0
2000
B - HA
Spirontocaris spinus
87
0.4
1.9
0.0
0.4
25
200
5
465
B - HA
Eualus fabricii
85
0.4
0.7
0.0
0.2
25
152
5
275
B - HA
Pandalus borealis
74
0.6
2.3
0.0
0.5
26
200
10
500
B - LA
Eualus belcheri
72
0.5
1.4
0.0
0.4
25
200
135
290
LA - HA
Lebbeus polaris
49
0.6
2.0
0.0
0.6
25
152
0
930
B - HA
Pandalus montagui
44
1.0
5.4
0.0
1.7
25
148
5
786
B - HA
Sclerocrangon boreas
23
2.0
6.4
0.3
2.1
25
59
0
400
B - HA
Sabinea septemcarinata
15
2.0
5.9
0.1
2.3
25
200
0
406
B - HA
Spirontocaris phippsii
15
0.3
1.0
0.0
0.4
26
99
10
270
B - HA
Eualus stoneyi
10
1.1
1.2
0.8
0.2
63
200
13
37
LA
B - HA
Eualus gaimardii
5
0.4
0.5
0.2
0.3
69
87
10
900
Spirontocaris lilljeborgii
5
0.2
0.2
0.1
0.1
59
82
20
1200
B - LA
Eualus macilentus
3
0.6
0.6
0.6
87
87
28
540
B - HA
B - HA
Lebbeus groenlandicus
3
2.8
2.8
2.8
59
59
2
314
Pisces
27
2.3
12.4
0.0
2.7
25
200
0
900
B - HA
Anisarchus medius
41
1.1
5.0
0.4
1.2
25
200
10
150
LA - HA
LA - HA
Icelus spatula
28
1.9
11.1
0.2
3.2
38
148
20
200
Hippoglossoides platessoides
21
6.8
17.1
0.8
6.1
38
107
0
700
B - HA
Gymnocanthus tricuspis
8
0.8
0.9
0.6
0.1
25
26
0
100
LA - HA
Icelus bicornis
8
1.2
2.7
0.0
1.3
53
87
2
560
B - HA
Leptoclinus maculatus
8
3.3
4.2
2.7
0.8
75
148
50
400
B - HA
Myoxocephalus scorpius
8
9.0
18.3
4.2
8.1
32
75
0
200
B - HA
Ulcina olrikii
5
0.3
0.3
0.2
0.1
38
53
40
100
LA - HA
Anarchichas lupus
3
4.2
4.2
4.2
152
152
20
300
B - LA
Anarchichas minor
3
12.8
12.8
12.8
145
145
~25
>500
B - LA
Artediellus atlanticus
3
6.6
6.6
6.6
75
75
100
800
B - LA
Aspidophoroides monopterygius
3
0.1
0.1
0.1
25
25
20
350
B - LA
Cyclopteropsis mcalpini
3
0.0
0.0
0.0
33
33
10
174
HA
Eumicrotremus spinosus
3
1.0
1.0
1.0
26
26
50
400
LA - HA
Leptagonus decagonus
3
1.3
1.3
1.3
152
152
150
900
LA - HA
Marine Science 2014, 4(1): 10-20
3.2. WP2 Net Samples
-3
The biomasses m obtained from WP2 net samples in
2008 were much lower than those from the sledge samples.
Total biomasses m-3 from the 29 WP2 net samples averaged
0.4 ± 0.4g m-3 while the total biomasses from the sledge
samples averaged 2.1 ± 1.7 g m-3. Caridea ≥ 5 mm were
found in only one 156 m haul (two P. borealis and one E.
belcheri (Table 2)). Only a few Hyperiidea juv. were found
(in 15 out of 29 WP2 net samples with a negligible biomass
of 0.002 ± 0.003 g m-3) in 25-152 m hauls. Although some
Euphausiacea were found in a few sledge samples from 2008,
none were found in the WP2 net samples.
Copepoda were found in all WP2 net samples - almost
exclusively Calanus species and for the most part C.
hyperboreus. The largest biomasses were obtained from the
50-100 m hauls and especially from the ~ 75 m hauls where
C. hyperboreus was most abundant (Figure 6B). Also the
sledge samples from 50-100 m depth yielded the greatest
Copepod biomasses m-3. This would seem to indicate that
Copepoda were most abundant near the bottom at 50-100 m
depth at this point in time. But this was not so, since the
sledge samples corresponding to the WP2 net samples
yielded, on average, a Copepod biomass m-3 which was 49 %
of the WP2 net samples (0-0.8 g compared to 0.015-1.6 g wet
weight m-3). Seven out of the 29 sledge samples were
virtually without Copepoda and 18 yielded a Copepod
biomass m-3 which was 0.3-35 % of the corresponding WP2
net samples. The remaining four sledge samples taken at
mean depths of 33-100 m yielded greater (1.5-2.5 times)
Copepod biomasses m-3 than the corresponding WP2 net
hauls from 48-116 m. But only for the 100 m sledge sample
was this biomass overweight due to an exceptionally high
Copepod biomass of 0.8 g m-3 (the greatest in any sledge
sample and 12 times the mean Copepod biomass m-3 for the
29 sledge samples - but only half of the largest WP2 net
sample Copepod biomass m-3). In the remaining three cases
the Copepod biomass overweight in the sledge samples was
due to a comparatively low Copepod biomass m-3 in the WP2
net samples (3.7-12 % of the WP2 net sample mean
compared to 20-71 % of the WP2 net sample mean for the
sledge samples).
4. Discussion
The primary purpose of this study was to quantify the
taxonomic groups and entities of the benthopelagic and
associated bottom-near pelagic fauna > 0.5 mm in and off the
bay Laksebugten off the south coast of Disko Island in the
northern part of Disko Bay, West Greenland with respect to
size, distribution, density, and biomass. The study focused
on sampling animals that were considered potential prey for
bowhead whales and efforts were aimed at identifying the
taxonomic groups that contribute the most to total biomass in
the area. Detailed studies of benthopelagic and associated
pelagic fauna in the Arctic are rare and none exist from
Greenland.
19
An epibenthic sledge (KC Denmark A/S) was used to
sample benthopelagic and associated pelagic animals living
close to the bottom. With some exceptions, the sledge
performed well and sampled consistently at the depth range
25-200 m. On some occasions, however, large rocks caused
the sledge to topple over and end upside down.
Benthopelagic and associated pelagic fauna is critical to
many food chains in the Arctic and quantification of animal
biomass and abundance provides an important insight into
the background for distribution and occurrence of several top
predators. Both abundance and diversity of benthopelagic
and associated pelagic invertebrates suggest that
Laksebugten is a highly productive area. This is also
supported by high concentrations of schooling fish (capelin
Mallotus villosus) in summer, large sea bird colonies (fulmar
Fulmarus glacialis, cormorant Phalacrocorax carbo, black
guillemot Cepphus grylle, kittiwake Rissa tridactyla), large
abundance of bowhead whales in late winter and spring, and
the occurrence in summer of several species of other large
baleen whales (fin whale Balaenoptera physalus, minke
whale Baleanoptera acutorostrata, humpback whale
Meganoptera novaeangliae) that generally use West
Greenland waters as a summer ground[12] and specifically
seek localities such as Disko Bay for feeding.
It is interesting to consider why waters in and off
Laksebugten, out of thousands of bays and inlets along the
coast of West Greenland, could have a particularly high
production with a rich benthopelagic and associated pelagic
fauna.[13] describes a cyclonal current in Disko Bay
receiving water from the West Greenland Current from the
south and occasionally, when this current is weak, from the
Baffin Current via the Vaigat (a strait to the north between
Disko Island and the Nuussuaq Peninsula). Water is extruded
northward through the Vaigat and/or westward, south of
Disko Island, passing by Laksebugten. Deep, relatively
high-saline and warm inflowing water from the West
Greenland Current mixes with less saline, locally cooled and
diluted intermediate water which in turn mixes with fresher
surface water, which is colder and not so diluted in winter
and warmer and more diluted in summer. According to[14]
much of the water leaving Disko Bay passes along the
southern coast of Disko Island as a highly stratified current,
especially in spring. Upwelling of nutrient-rich deep West
Greenland Current water driven by the melting of icebergs
and glaciers is the basis for exceptionally high primary
productivity in the north-eastern part of the bay and in the
outgoing current, especially in spring when sea ice no longer
blocks out sunlight[3]. Later in the year, production intensity
tapers off due to surface mixing and surface layers being
depleted of nutrients as the current flows out of Disko Bay.
Production is generally higher in the northern part of the bay
mouth near Disko Island and Qeqertarsuaq than in the
southern part near the mainland and Aasiaat.
Copepoda, notably Calanus species that diapause in
deeper water, are primary prey animals of bowhead whales.
Adults and eggs of some Calanus rise to the surface to
propagate and hatch during the spring bloom[5][6]. Here
20
Ole Gorm Norden Andersen et al.: Benthopelagic Shrimp and Associated Pelagic and Benthopelagic
Fauna on a Bowhead Whale Foraging Ground in Disko Bay, West Greenland
they feed into the shallow benthopelagic community in
Laksebugten and contribute to the production in this area.
Stomach contents from bowhead whales caught in
Alaskan waters[15] included 136 faunal entities (family,
gender, species), of which 92 were benthic or benthopelagic,
including 11 Caridea and 11 Pisces. In this study, 15 species
of Caridea and 15 species of Pisces were identified in the
sledge samples from Laksebugten and were thus available to
bowhead whales. The stomach contents from two bowhead
whales caught in Disko Bay in May 2009 included ~ 99 %
Copepoda (by both weight and number), similar to the
content of several WP2 net samples from the upper 15 m in
Disko Bay in 2009. These two whales, therefore, did not
target the benthopelagic and associated pelagic fauna in the
area.
5. Conclusions
Although a rich benthopelagic and associated pelagic
fauna was found in the foraging area, further studies of
bowhead feeding are needed to elucidate to what extent this
potential food source in Laksebugten and adjacent areas is
included in the late winter and spring diet of bowhead whales
in West Greenland.
ACKNOWLEDGEMENTS
This study was funded by the Commission for Scientific
Research in Greenland (IPY funding), by the US National
Ocean Partnership Program (Office of Naval Research and
US National Science Foundation) and by the Greenland
Institute of Natural Resources. The University of
Copenhagen kindly provided access to their facilities
including r/v Porsild in Qeqertarsuaq.
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